The semi truck hit about 28 cars and trucks along Interstate 70 on Thursday near Denver, killing at least four people and leaving several others injured, police said.

Aguilera-Mederos, 23, is being held on four counts of vehicular homicide in connection with the crash. He briefly appeared in court Saturday and a judge ordered his bond to be set at $400,000. Formal charges have not yet been filed, pending the results of the investigation.

Investigators say Aguilera-Mederos told them he was driving at 85 mph when the brakes failed. He tried to pull over to the shoulder to avoid stopped traffic but another semi had stopped there, an arrest affidavit shows.

“Rogel said he thought he was going to die so he closed his eyes before hitting the stopped traffic,” the document states.

A witness told police that prior to the crash, he noticed something was wrong when he saw Aguilera-Mederos “wide eyed” and “with a terrified look on his face,” the affidavit states.

On Sunday, Jefferson County Coroner’s Office identified the crash victims as four Colorado men. Doyle Harrison, 61, of Hudson; William Bailey, 67, of Arvada; Miguel Angel Lamas Arrellano, 24, of Denver; and Stanley Politano, 69, of Arvada all died in the crash, the coroner’s office said.

The causes of deaths are pending further studies but the autopsies have been completed, the coroner’s office said in a news release.

After Saturday’s court hearing, Robert Corry, an attorney representing Aguilera-Mederos, said his client was in “deep sorrow” and was cooperating with police.

“It cannot be overstated, the degree to which he feels sorrow for this absolutely tragic accident,” Corry said. “Everybody agrees it was an accident. Law enforcement agrees it was an accident. Everybody who has been investigating or has looked at it believes it was an accident, and it’s tragic.”

Authorities had said there was no evidence of drugs or alcohol in the crash.

Lakewood Police Department Agent Ty Countryman said investigators are looking into whether there were any mechanical issues with the truck, but said he believed that vehicular manslaughter charges would still stick if a mechanical issue is confirmed.

Aguilera-Mederos has a commercial driver’s license from Texas. The suspect’s brother, Daniel Aguilera, said Rogel is Cuban and is a permanent resident of the United States.

‘Startled and in shock’

People crawled out of the vehicles and pulled out those who were trapped as flames shot up the wreckage surrounded by piles of lumber.

The victims died while trapped in their vehicles and their remains were beyond recognition, court documents said.

Josh McCutcheon, who caught the crash on video, told CNN sister network HLN he had never seen such devastation. He’s doing fine now, he said, but he was “startled and in shock” when he saw the deadly pileup, the explosions and the plumes of smoke.

“Oh, my God,” he shouted when it happened.

McCutcheon praised a “good Samaritan” for pulling people out of cars.

“That’s a true hero,” he said of the man, who had been panhandling in the area.

Darin Barton was panhandling near the scene when the crash happened. He told CNN affiliate KDVR that when the cab of the truck rolled over and flames ignited, he quickly dropped the sign he was holding and ran toward the cars.

“It just caught on fire. And I just dropped my sign, took off running,” Barton said. “As soon as I (saw) flames, I headed under the bridge, grabbed three or four people out of a couple cars.”

It’s unclear what made the vehicles ignite, Countryman has said, adding that he does not know what was in the semis other than the one that appeared to be carrying lumber.

“This is looking to be one of the worst accidents we’ve had here in Lakewood,” he said.

The Denver West Parkway bridge over I-70 sustained significant structural damage from the fire, authorities said.